Underdrain for trickling filters



W. P. RAWN UNDERDRAIN FOR TRICKLING FILTERS Filed Nov. 10, 1924 2 Sheets-Sheet l 1 n" a. 7/- -J l\ /b/ 6 4/ n n .n f @I L i c il Tus.. Il [L jl i-' 1:4 YI". 1 l.. |||l ll'rllu il 15V-.. L al 4 l El. vl Tf.. il. inI ---L 'i -l I |n l. l P,..- Tvjx n TIA .--L 1J lt Ti.. 1-21--; w 0/ 4 l.

l La, 6,114 QM. 67705/1/725 May 1l 1926. 1,584,142

W. P. RAWN UNDEHDRAIN Fon TRICKLING FILTERS Filed Nov. 10 1924 2 Sheets-Sheet 2 Patented May 11, 1926. l UNITED STATES PATENT OFFICE.

IWILLIAM P. RAWN, 0F WASHINGTON, IOWA,` ABSIGNOR OF ONE-THIRD T0 E. G. NELSON AND ONE-THIRD T0 A. J. LAESON, 0F WHAT CREER, IOWA.

UNDERDBAIN FOB. TRICKLING FILTERS.

Application led November 10, 1924. Serial No. 748,879.

My invention relates broadly to sewage treatment, and has special reference to an improved underdrain for trickling filter permitting efficient filtration without putrefaction of the organic matter.

Briefiy my invention distinguishes from the prior art b an efficient and simplified construction. t is commonly known that in the treatment or purification of sewage the purity of the efliuent resulting from downward intermittent filtration depends on a biological action requiring an efficient supply of oxygen. In the absence of such supply, brought into contact with the efiiuent, oxidation of the organic matter fails and offensive odors are produced during filtration. I have found that oxidation changes the organic matter into either a mineral or stable organic matter, which, under ordinary conditions, do not undergo any change giving up undesirable odors.

During the sewage treatment, bacterial jelly adheres to the surfaces of the filtering material. When in a mature condition, the filtering material will be found to be coated from top to bottom by the bacterial jelly. The dissolved organic'matter in the liquid sewage is either absorbed by the bacterial jelly, or acted upon directly. It has been noticed that there is a periodic storage and disgorging of these transformed solids, and, if a free passage is-not provided, the system must be shut off and the filtering 'material removed and cleaned. It may be mentioned that the periodic disgorging of the solids is due to a community of innumerable living organisms being affected by the seasons an responding quickly to temperature changes. Heretofore in the art, difficulty has been experienced in properly providin for a free passage of the transformed soli s. Furthermore, difficulty has been experienced in providing an adequate and efficient supply of oxygen during the period in which the organic matter is undergoing a change to mineral or stable organic matter, with the result that undesirable and offensive odors would be given off. So far as I am aware, the prior art in construction of trickling filters for sewage treatment provided as drainage and air supply a plurality of inverted U-sha ed tile blocks spaced apart a predetermined istance to permit the air below to permeate upwardly through the filtering material. The chief difficulty with such a construction is that the bacterial jelly and other matter together with the liquid filterin through clogs and spreads over the fioor o the filter in and between the tile to a uniform depth, thereby covering the space between the tiles and cutting off all circulation of air from below. Moreover, no defined flow could result and the entire system was incapable of being flushed, particularly when the solids were disgorged.

Primarily, the obj ect of my invention is to obviate the above difliculties and includes the provision of improved tile blocks in the form of troughs which allow efficient circulation of air through the filtering material and an open assage leading to the discharge pipe of the lter for the li uid and transformed solids. A further o ject is to construct the troughs in a novel manner so as to obtain rapid discharge of the efiiuent therefrom. This is obtained by forming the surface of the trou hs circular `or like the lower half of a horizontal tube in order to obtain a minimum surface contact and a resultant increased velocity flow. A further objectof my invention consists in the manner in which the trou hs are supported, and further in the fact t at the ends are thereby provided open so that inspection and cleaning may be permitted without requiring removal from their foundation. I prefer to provide them permanently embedded in concrete, so that the underdrain construction will be of a permanent character for securely maintaining the tile in place.

With the forms of construction heretofore used in the art the alignment of the channels has been difficult or impossible to attain, and in the pro ress of construction the placing of the ltering material shifts the troughs or tiles out of line forming an impediment to flow of liquids, and impairing the eflicient operation of the drain. In then construction of a filter using my invention, Iprefer to place the series of troughs end to end upon the floor or base (provided, spacing the same laterally a pre etermined distance, and the construction of the troughs is such as to permit securing definite and permanent alignment thereof. By the use of the troughs with the lateral extension 18 at bottom of base the concrete poured between the trou hs will be superimposed u on the lateral proJections 18 and thus avoiding floating or disturbing the troughs during construction. If construction be attempted b the use of U-shaped troughs substantially li e the trough herein described without the lateral projections forming parts of the base, there will be a tendency to float or disturb the troughs when the concrete is poured between them. After the troughs and channels are imbedded in the concrete and the concrete has set to permit further work, the channels are cleaned and l e material removed therefrom, then the cover plates are placed, insuring clean open drainage channels before the `filtering material is placed thereon.

A further feature of my invention consists in the provision of apertured plates over the trou hs which form the cover and support for ltering material.

I further desire to provide the apertures with an upward taper, so that material passing therethrough will not tend temporarily to clog the apertures. The following advantages are the result of my invention:

(A) An abundant air supply for the filtering materialz and consequently, the assurance of a biological action, which will prevent utrefaction; l

B) rompt and free discharge of hqui s, avoiding pending or stagnation thereof in the filter;

(C) Provision of a definite passage throu h the filtering'` bed, for air and for the euent or liquids to be treated;

D) Freedom from clogging; 2E Accessibility for cleaning; and

(Fi A simple and durable underdrain trickling filter, capable of functioning efficiently at all times.

In order to apprise those skilled in the art how to construct and practice my invention, I shall nowdescribe an embodiment thereof in connection with the accompanyin drawings which form a part hereof.

,gin the drawings:

Figure 1 is a top plan view of a trickling filter underdrain construction embodying my invention;

Fig. 2 is a vertical sectional view taken onV line 2--2 in Fig. 1;

Fig. 3 is an enlarged cross-sectional view illustrating the manner of embedding the tile troughs ,in concrete; and

Fig. 4 is a top view thereof. On .the right of the drawing is shown one form of suitable construction of the cover plate, and on the left of the drawing is shown another suitable form of such cover late.

As illustrated in the rawings, the trickling filter com rises a filtering bed 3 having the end wa ls 4 and 5 and the side walls 6 and 7. The walls are preferabl formed integrally with a door 8. If so esired, a sludge dryin bed 9 may be rovided adjacent the si e wa1l46 for receiving sludge that has been removed from the sewage in the primary treatment tanks. At the ends of the filtering bed, ins ction galleries 10 and 11 are rovided. Th2 efliiient from the tricliling fi ter is collected by the underdrain s stem and is discharged into ins ection ga lery 11, which is so constructs as to drain to outlet sewer 28. Inspection allery 10 is used, also, as a place to introiuce iushing appliances into underdrain. Ef-

fluent from plrimary treatment tanks is conducted to t e filtering bed by means of a pipe 12 communicatin with suitable spray nozzles 13 by means o the connections 14. and branch pipes l5.

As illustrated in Fig. 3, the underdrain construction com rises a plurality of tile troughs 17 place end to end to form underdrain channels which are arranged in rows and communicate with the inspection galleries 10 and 11. Tile troughs 17 are referably U-shaped and are furnished with eet 18 which rest on a bed of mortar 19 poured along the floor 8. Concrete 2O is then cured between the tile troughs and is broug ft ush with the top of the troughs. Hence, the tile troughs 17 are solidly einbedded in the concrete. Shoulders 21 are rovided along the inner side of the troughs or receiving a plurality of cover plates 22. These plates are preferably flush with the to s of the troughs and the coicrete so that a at surface may be presentedV to the filtering material 25 illustrated in Fig. 3. Apertures 26 are provided in plates 22 and are tapered upwardly so as to present the smaller en of the opening kto the filtering material. With these apertures formed in this manner, I find that it is impossible for any of the transformed solids, when periodically disgorged from the filtering material, to clog the apertures 26. Moreover, the effluent filtering downwardly through the filtering material finds a quick passage into the tile troughs. The fore oing is descriptive of the construction s own on left side of Fi 4. If the construction shown on right side of Fig. 4 is used, the apertures are formed by the shaping of the pieces used. These pieces are suitab y formed and set side by side on the shoulders 21. I preferably provide the interior surface of the trough 17 semi-circular so that its contacting area ma -be reduced to a minimum .to increase t e velocity of fiow. This is particularly desirable when the underdrain construction is flush, say at a time when the transformed solids are unloaded from the filtering material, inasmuch as a rapid and continuous flow is preferable to carry ofi` all uicl and matter from the channels to revent clogging. This is true at any time, owever, as the water within the channel should never stand, nor rise to a level which would prevent a circulation of air below the plates 22.` It will be noted in Fig. i

the parallel channels 27, formed by the tile troughs 17 being placed end to end, open into both inspection galleries 10 and 11, but they preferably drain into the gallery 11, which is provided with a drain pipe 28.

The tile covers 22 may be temporarily secured in position by cement 30. As illustrated in Fig. 4, these covers may be spaced a slight distance apart in order to provide openings 31 which assist in the drainage of the effluent and also the transformed solids from the filtering `material in the troughs 17. By this arrangement, the circulation of air from below into the filterin material 25 is facilitated, so that a sufficient supply of oxygen is assured. By providing the interior of the channels semi-circular and thereby increasing the fiow into the inspection gallery 11, I find that there will not be a tendency for the water to rise to a height within the tile channels which prevents the air from entering at the ends of the channels and continuously feeding upwardly through the apertures QG and the spaces between Athe cover plates 22. The inspection galleries 10 and 11 allow the attendant to look through the channels from the ends for inspection, thereby ascertaining whether the same are being clogged by any solid material that has assed from the filtering material 25 throng the openings 26 or spaces 31 between the cover lates.

Without further "elaboration, t e foregoing will so fully explain the gist of my invention that others may, by applying current knowledge, readily adapt the same for use under varying conditions of service, without eliminating certain features which may properly be said to constitute the essential items of novelty involved, which items are intended to be defined and secured to me by the following `claimsr I claim:

1. An underdrain construction comprising a floor, a series of troughs placed end to end upon said floor to form a drain channel, and a series of flat covers disposed relativel flush with and placed to cover said channe said covers being apertured to permit liquids to drain therethrough into said troughs and to admit air from said troughs to the material supported above said covers, the area at the sides of said channel being filled to the height of the top of said covers with substantially non-permeable material.

2. An underdrain construction comprising a floor, a series of troughs placed end to end upon said floor to form a drain channel, and a series `of covers of kiln-burned or concreted material placed to cover said channel, said covers being apertured to permit liquids to drain therethrough into said troughs and to admit air from Said troughs to the material supported above said covers, said channels being straight and open from end to end to facilitate inspection and cleaning and being accessible without disturbing the material above the channels.

3. An underdrain construction comprising a floor, a series of troughs placed end to end upon said Hoor to form a drain channel, and a series of covers placed to cover said channel, said covers being apertured to permit liquids to drain therethrough into said troughs and to admit air from the troughs to material supported above said covers, the area at the sides of said channel being filled to the height of the top of said covers with substantially non-permeable material, said channels bein straight and open from end to end to facllitate inspection and cleaning and being accessible without disturbing the `material above said channels.

4. An underdrain construction comprising a floor, a series of troughs placed end to end upon said ioor to form a drain channel, and a series of covers placed to cover said channel, said covers being apertured to permit liquids to drain therethrough into said troughs and to admit air from said troughs to the material supported above said covers` the sides of said troughs having shoulders for supporting said covers so that the upper surface of said covers is substantially flush with the to s of the troughs.

5. An un erdrain construction comprising a Hoor, a series of troughs placed end to end upon said floor to form a drain channel, and a series of covers placed to cover said channel, said covers being apertured to permit liquids to drain therethrough into said troughs and to admit air from the troughs to the material supported above said covers. the area at the sides of said channel being filled to the hei ht of the top of said covers with substantie ly non-permeable material, the sides of said troughs having shoulders for supporting said covers so that the u per surface of said covers is substantially ush with the top of the troughs.

6. An underdrain construction comprising a floor, a series of troughs placed end to end upon said floor to form a drain channel, and a series of covers'placed to cover said channel, said covers being a ertured to permit liquids to drain theret rough into the troughs and to admit air from said troughs to the material supported above said covers, the area at the sides of said channel being filled to the hei ht of the top of said covers with substantialflly non-permeable` material, said troughs being so constructed as to provide each with a base or solid bearing surface to prevent its tipping or rolling while being imbedded.

7. An underdrainconstruction comprlsing a floor, a series of troughs placed end to end upon said floor to form a drain channel, and a series of covers laced to cover said channel, said covers ing apertured to permit liquids to drain therethrough into said troughs and to admit air from said troughs to the material supported above said covers, the area at the sides of said channel being filled to the height of the top of said covers with substantially non-permeable material. the said troughs being so' constructed as to provide each with a base having portions projecting laterally below a concave periphery.

8. An underdrain construction comprisinv a floor, a series of troughs placed end to end upon said floor to form a plurality of drain channels, and a series of covers placed to cover said channels, said covers being spaced apart a predetermined distance to permit liquids to drain therethrough into said troughs and to admit air from the troughs to the material supported above the covers.

9. An underdrain construction for a trickling filter comprising a filtering bed support upon which filtering material is adapted to be placed, a plurality of troughs forming underdrain channels permanently imbedded in and disposed below the surface of said support whereby the etlluent or other substances will drain directly into the troughs.

10. An underdrain construction for a trickling filter comprising a filtering bed support upon which filtering materlal is adapted to be placed, a plurality of troughs forming underdrain channels permanently' imbedded in and disposed below the surface of said support whereby the effluent or other substances will drain directly into the troughs, and a gallery at one end of said filtering bed into which said troughs are adapted to drain.

11. An underdrain construction for a trickling filter comprising a filtering bed support, a plurality of troughs forming underdrain channels disposed in permanent relation below the surface of said support and apertured covers for said troughs.

12. An underdrain construction for a trickling filter, comprising a filtering bed support, a plurality of troughs forming underdrain channels dis osed in rmanent relation below the sur ace of sai support, and covers for said channels, said covers being provided with upwardly tapered apertures.

13. An underdrain construction for a triclrling filter, comprising a filtering bed support upon which filtering materlal is adapted to be placed, a plurality of troughs forming underdrain channels imbedded in and disposed below the surface of said support whereby the etliuent or other substances will drain directly into the troughs, and galleries into which both ends of said channels open.

14. A trough adapted for use in an underdrain construction for a trickling filter comprising a U-shaped bodyr portion provided with oppositely disposed shoulders along the interior edges, and an apertured cover plate for seating on said shoulders, said cover plate being flush with the top of said trough.

WILLIAM P. RAW'N.

liquids to drain therethrough into said troughs and to admit air from said troughs to the material supported above said covers, the area at the sides of said channel being filled to the height of the top of said covers With substantially non-permeable material. the said troughs being so constructed as to provide each with a base having portions projecting laterally below a concave periphery.

8. An underdrain construction comprisinoi a floor, a series of troughs placed end to en, upon said Hoor to form a plurality of drain channels, and a series of covers placed to cover said channels, said covers being spaced apart a predetermined distance to permit liquids to drain therethrough into said troughs and to admit air from the troughs to the material supported above the covers.

9. An underdrain construction for a triekling filter comprising a filtering bed support upon which filtering material is adapted to be placed, a plurality of troughs forming underdrain channels permanently imbedded in and disposed below the surface of said support whereby the eflluent or other substances will drain directly into the troughs.

10. An underdrain construction for a trickling filter comprising a filterin bed support upon which filtering materlal is adapted to be placed, a plurality of troughs forming underdrain channels permanently imbedded in and disposed below the surface of said support whereby the effluent or other substances will drain directlyT into the troughs, and a gallery at one end of said filtering bed into which said troughs are adapted to drain.

11. An underdrain construction for a trickling filter comprising a filtering bed support, a plurality of troughs forming underdrain channels disposed in permanent relation below thesurface of said support and apertured covers for said troughs.

12. An underdrain construction for a trickling lter, comprising a filtering bed support, a pllurality of trou hs forming underdrain c annels dis ose in rmanent relation below the sur ace of sai support, and covers for said channels, said covers being provided with upwardly tapered apertures.

13. An underdrain construction for a trickling filter, comprising a filtering bed support upon which filtering material is adapted to be placed, a plurality of troughs forming underdrain channels imbedded in and disposed below the surface of said support whereby the eiiluent or other substances will drain directly into the troughs, and galleries into which both ends of said channels o en.

I)14. A trough adapted for use in an underdrain construction for a trickling lter comprising a U-shaped body portion provided with oppositely disposed shoulders along the interior edges, and an a ertured cover plate for seating on said s oulders, said cover plate being flush with the top of said trough.

WILLIAM P. RAWN.

cerner-pte of Gutmann,

It is hereby uponthe ap ii ment in ont the words that in Letters Patent No. 1,584,142, r ion of William P. Rawn, of Washington, 'owayfor an unprOV- nderdrains for Trickling Filters, 'spieation reguiringcorrec-tion as follows: Page of kiln-burned or oonore'ted mater1a1; 'Patent shouldbe4 read with this/correction therein that the same may anted May 11, 1926,

an error appears in the printed 3, lines 59 and 60, claim 2, strike and that the said Letters conform to therecord, ofthecase in the PatentOice.

Sismi 11161 Med *#hlth {SNI-dl n day 'of June, A. 1926.- i .l

A M, J. Moons,

At/ng C'ormmimmerr of Patents.

cmifiate of cortion.

It is hereby rfjifid mi, in Letters Pfnt No. 1,584,142, )grant/ad May 11, 1926, uponthe ap lcation of William?. Rawn, of Washington, owa, -for an impiovement in nderdrains for Trickling Filters, an error rippen-'rs 1n the printed 'speqiiicabion r ur'ingcorection as follows: Page 3, lines 59 sind 60, claim 2, strike dnt the words of kiln-burned or concreted material and that the said Letters P ant shmdbqrd with thismorrention therein that the same may conform to thev moordr caitho ca'se in tho Patntoice.

s .ncI sealed thisvlth day o'June, A. D. 1926. [aan] M. J. MOORE.,

dirti/ng Uomvndoner of Patents. 

